I am a bit a bit puzzled, but I don’t know what to expect from this system + setup. Do you have any other fullscreen OpenGL non-GLFW apps you can test with?
It might also be worth checking that you’re setting the same mode (bits as well as refresh rate):
const GLFWvidmode* mode = glfwGetVideoMode(monitor);
glfwWindowHint(GLFW_RED_BITS, mode->redBits);
glfwWindowHint(GLFW_GREEN_BITS, mode->greenBits);
glfwWindowHint(GLFW_BLUE_BITS, mode->blueBits);
glfwWindowHint(GLFW_REFRESH_RATE, mode->refreshRate);
GLFWwindow* window = glfwCreateWindow(mode->width, mode->height, "My Title", monitor, NULL);